samedi 6 juin 2015

LHC experiments back in business at record energy

CERN - European Organization for Nuclear Research logo.

June 6, 2015

Image above: Collisions seen within the ALICE experiment's detector (Image: ALICE/CERN).

The Large Hadron Collider (LHC) started delivering physics data today for the first time in 27 months. After an almost two year shutdown and several months re-commissioning, the LHC is now providing collisions to all of its experiments at the unprecedented energy of 13 TeV, almost double the collision energy of its first run. This marks the start of season 2 at the LHC, opening the way to new discoveries. The LHC will now run round the clock for the next three years.

Image above: In the CERN Control Centre, the LHC operations team as well as members of CERN management applaud the announcement of stable beams this morning at 10.40am (Image: Maximilien Brice/CERN).

Image above: Display of proton-proton collision events recorded by ATLAS on 3 June 2015, with the first LHC stable beams at a collision energy of 13 TeV. Tracks reconstructed from hits in the inner tracking detector are shown as arcs curving in the solenoidal magnetic field. The green and yellow bars indicate energy deposits in the liquid argon and scintillating-tile calorimeters. (Image ATLAS/CERN).

“With the LHC back in the collision-production mode, we celebrate the end of two months of beam commissioning,” said CERN Director of Accelerators and Technology Frédérick Bordry. “It is a great accomplishment and a rewarding moment for all of the teams involved in the work performed during the long shutdown of the LHC, in the powering tests and in the beam commissioning process. All these people have dedicated so much of their time to making this happen.”

Image above: Collisions as seen within the LHCb experiment's detector (Image: LHCb/CERN).

On 3 June 2015 at 10.40am, the LHC operators declared “stable beams”, the signal for the LHC experiments that they can start taking data. Beams are made of “trains” of proton bunches moving at almost the speed of light around the 27 kilometre ring of the LHC. These so-called bunch trains circulate in opposite directions, guided by powerful superconducting magnets. Today the LHC was filled with 6 bunches each containing around 100 billion protons. This rate will be progressively increased as the run goes on to 2808 bunches per beam, allowing the LHC to produce up to 1 billion collisions per second.

Image above: Collisions seen within the CMS experiment's detector (Image: CMS/CERN).

For more information see the live blog that covered events as they unfolded:

See a gallery of images from the day:


CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

Related link:

Large Hadron Collider (LHC):

For more information about the European Organization for Nuclear Research (CERN), visit:

Images (mentioned), Text, Credits: CERN/Cian O'Luanaigh.


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